Physical Chemistry of Macromolecules employs the combined principles of physical chemistry to define the behaviour, structure, and intermolecular effects of macromolecules in both solution and bulk states. It emphasizes the statistical measures of structure and weight distribution, and also discusses structural, dynamic, and optical properties of macromolecules in solution.

Theoretical chemistry is the discipline that uses quantum mechanics, classical mechanics, and statistical mechanics to explain the structures and dynamics of chemical systems and to correlate, understand, and predict their thermodynamic and kinetic properties. Modern theoretical chemistry may be roughly divided into the study of chemical structure and the study of chemical dynamics. The former includes studies of: (a) electronic structure, potential energy surfaces, and force fields; (b) vibrational-rotational motion; and (c) equilibrium properties of condensed-phase systems and macro-molecules. Chemical dynamics includes: (a) bimolecular kinetics and the collision theory of reactions and energy transfer; (b) unimolecular rate theory and metastable states; and (c) condensed-phase and macromolecular aspects of dynamics.

Chemistry, by its very nature, is related with change. Substances with well-defined properties are converted by chemical reactions into other substances with distinct properties. For any chemical reaction, chemists try to find out the practicality of a chemical reaction which can be predicted by thermodynamics, extent to which a reaction will continue can be determined from chemical equilibrium and speed of a reaction i.e. time taken by a reaction to reach equilibrium. Along with viability and extent, it is equally important to know the rate and the factors controlling the rate of a chemical reaction for its thorough understanding. For example, which parameters determine as to how rapidly food gets spoiled? How to design a rapidly setting material for dental filling? Or what controls the rate at which fuel ignites in an auto engine? All these questions can be answered by the branch of chemistry, which deals with the study of reaction rates and their mechanisms, called chemical kinetics.

Chemical physics is a sub field of chemistry and physics that investigates physicochemical phenomena using techniques from molecular and atomic physics and condensed matter physics; it is the branch of physics that studies chemical processes from the point of perspective of physics. While at the interface of physics and chemistry, chemical physics is distinct from physical chemistry in that it focuses more on the typical elements and theories of physics. Meanwhile, physical chemistry observes the physical nature of chemistry. Nonetheless, the distinction between the two fields is vague, and workers usually practice in both fields during the course of their research.

Radiation chemistry indicates the chemical effects of interactions of ionizing radiation with materials. The term ionizing radiation in a wider perception is also applied to photons or particles having sufficient energy to ionize the molecules of the medium: it involves photons with energies differ from the first ionization energy of the medium (~ 10 eV) up to some million eV (MeV), as well as energetic charged particles, electrons, positrons, accelerated heavy ions, etc. In a narrower perception, only those radiations are considered in radiation chemistry, whose energies are several series of magnitude higher than the energies of the chemical bonds. The result of the energy absorption is breaking or rearrangement of chemical bonds; i.e. decomposition of some of the beginning molecules and formation of new ones. High-energy photons, charged species with adequately high energy and neutrons might be absorbed by the nuclei and cause nuclear reactions.

Femtochemistry is the field of physical chemistry that studies chemical reactions on extremely short timescales, about 10−15 seconds. The steps in some reactions occur in the femtosecond timescale and sometimes in attosecond timescales, and will few times form intermediate products. These intermediate products cannot always be concluded from observing the starting and end products. Femtochemistry enables exploration of which chemical reactions take place, and investigates why few reactions occur but not others. The resolution in time of the elementary dynamics (femtochemistry) offers an opportunity to observe a molecular system in the continuous process of its evolution from reactants to transition states and then to products. Application of femtochemistry in biological studies has helped to elucidate the conformational dynamics of stem-loop RNA structures.

Geochemistry is the science that utilizes the tools and principles of chemistry to explain the mechanisms behind significant geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the entire Solar System and has made significant contributions to the understanding of a number of procedures including mantle convection, the formation of planets and the origins of granite and basalt.

Astrochemistry is the study of chemical constituents found in outer space, generally on larger scales than the Solar System, especially in molecular gas clouds, and the study of their formation, interaction and destruction. As such, it represents an overlap of the areas of astronomy and chemistry. On the Solar System scale, the study of chemical elements is usually called cosmochemistry.

The study of chemical reactions, isomerizations and physical behavior that may occur under the influence of visible and/or ultraviolet light is known as Photochemistry. Photochemistry is the underlying mechanism for all of photobiology. When a molecule absorbs a photon of light, its electronic constitution changes, and it reacts differently with other molecules. The energy that is absorbed from light can effect in photochemical changes in the absorbing molecule, or in an adjacent molecule (e.g., photosensitization). The energy can also be set off as heat, or as lower energy light, i.e., fluorescence or phosphorescence, in order to    give back the molecule to its ground state. Each type of molecule has a different preference for which of these different mechanisms it utilizes to get rid of absorbed photon energy, e.g., some prefer fluorescence over chemistry.

Solid-state chemistry, also sometimes mentioned to as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials, peculiarly, but not necessarily exclusively of, non-molecular solids. Solid-state chemistry continues to play an amplifying role in an astounding array of disciplines. As the discovery of new physical phenomena has often depended on the progression of new materials, the synthesis of new solid-state materials and kinetically solid composites with optimized properties is of central importance. While solid-state materials have historically been developed through high temperature solid-state reactions, generally affording the most thermodynamically stable phases, a variety of techniques have been developed to master the limitations inherent in this traditional approach.

Spectroscopy is study of the absorption and emission of light and other radiation by matter, as related to the dependence of these procedures on the wavelength of the radiation. More recently, the definition has been expanded to include the study of the relations between particles such as electrons, protons, and ions, as well as their interaction with other particles as a role of their collision energy. Spectroscopic analysis has been crucial in the development of the most fundamental hypothesis in physics, including quantum mechanics, the special and general theories of relativity, and quantum electrodynamics. Spectroscopy, as applied to high-energy collisions, has been a key tool in developing scientific consideration not only of the electromagnetic force but also of the strong and weak nuclear forces.

Surface science is the study of physical and chemical phenomenon that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of surface chemistry and surface physics. Surface chemistry can be roughly defined as the study of chemical reactions at interfaces. It is closely associated to surface engineering, which aims at modifying the chemical composition of a surface by incorporation of selected elements or functional groups that generate various desired effects or improvements in the properties of the surface or interface. Surface science is of specific importance to the fields of heterogeneous catalysis, electrochemistry, and geochemistry.

Quantum chemistry is a field of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems. It is also known as molecular quantum mechanics. Quantum chemistry is the application of quantum mechanical theories and equations to the study of molecules. In order to understand matter at its most fundamental measure, we must utilize quantum mechanical models and methods. There are two aspects of quantum mechanics that make it differ from previous models of matter. The first is the concept of wave-particle duality; that is, the notion that we want to think of very small objects (such as electrons) as having characteristics of both particles and waves. Second, quantum mechanical models precisely predict that the energy of atoms and molecules is always quantized, meaning that they may have only certain amounts of energy. Quantum chemical theories allow us to elucidate the structure of the periodic table, and quantum chemical calculations allow us to accurately predict the structures of molecules and the spectroscopic behaviour of atoms and molecules.

Thermochemistry is the study of the heat liberated or absorbed as a result of chemical reactions. It is a branch of thermodynamics and is used by a wide range of scientists and engineers. Thermochemistry focuses on these energy changes, particularly on the system's energy exchange with its surroundings. For example, biochemists use thermochemistry to understand bioenergetics, whereas chemical engineers apply thermochemistry to depict manufacturing plants. Chemical reactions involve the conversion of a set of substances inclusively referred to as "reactants" to a set of substances collectively referred to as "products."

Biophysical chemistry is a physical science that uses the concepts of physics and physical chemistry for the study of biological systems. The most common feature of the research in this subject is to seek explanation of the various phenomena in biological systems in terms of either the molecules that make up the system or the supra-molecular structure of these systems. Biophysical chemists employ various techniques used in physical chemistry to probe the structure of biological systems. These techniques include spectroscopic methods such as nuclear magnetic resonance (NMR) and X-ray diffraction.

Physical chemistry is the study of the link between structure and reactivity of organic molecules. a lot of specifically, modern physical chemistry applies the experimental tools of chemistry to the study of the structure of organic molecules and provides a theoretical framework that interprets however structure influences each mechanisms and rates of organic reactions. It will be thought of as a subfield that bridges organic chemistry with physical chemistry. Physical organic chemists use each experimental and theoretical disciplines like spectrum analysis, chemical analysis, natural philosophy, and process chemistry, and scientific theory to check each the rates of organic reactions and also the relative chemical stability of the beginning materials, transition states, and product. Chemists during this field work to know the physical underpinnings of chemistry, and thus physical chemistry applications in specialised areas as well as chemical compound chemistry, supramolecular chemistry, chemical science, and chemical science.